Living organisms in any biome interact through a variety of relationships. Organisms compete for food, water, and other resources. Predators hunt their prey. Some organisms coexist in mutually beneficial relationships (symbiosis), while others harm organisms for their own benefit (parasitism). Still others benefit from a relationship that neither helps nor harms the other organism (commensalism).
Animals found in the Arctic tundra include herbivorous mammals (lemmings, voles, caribou, arctic hares, and squirrels), carnivorous mammals (arctic foxes, wolves, and polar bears), fish (cod, flatfish, salmon, and trout), insects (mosquitoes, flies, moths, grasshoppers, and blackflies), and birds (ravens, snow buntings, falcons, loons, sandpipers, terns, and gulls). Reptiles and amphibians are absent because of the extremely cold temperatures. While many of the mammals have adaptations that enable them to survive the long cold winters and to breed and raise young quickly during the short summers, most birds and some mammals migrate south during the winter
It is usually easier to calculate an enzyme's reaction velocity from the rate of appearance of PRODUCT rather than the rate of disappearance of a SUBSTRATE. Enzyme activity is measured as an INITIAL reaction velocity, the velocity before much SUBSTRATE has been depleted and before much PRODUCT has been generated. It is easier to measure the appearance of a small amount of PRODUCT from a baseline of zero PRODUCT than to measure the disappearance of small amount of SUBSTRATE against a background of high concentration of SUBSTRATE.
Biomagnification is the name given to the progressive accumulation of substances from one trophic level to another along a food chain. Thus, the substance will have its highest concentration in individuals who occupy trophic levels furthest from producers.
For biomagnification to occur, substances must be fat soluble (lipid soluble) and thus adhere to living tissues. Another feature of substances that undergo biomagnification is that they are generally not biodegradable or metabolized by the body.
The phenomenon is quite common with heavy metals (lead; mercury) and certain chlorinated and aromatic organic compounds with higher molecular mass, such as the insecticide DDT.
Evolution is a process of elimination. the traits that are successful and help them survive are kept for the next population, because they are abet o survive to repopulate. So its improvement.
